a) Field of the Invention
The invention concerns a receiver and a transmitter for a wireless transmission system.
b) Description of the Related Art
In the case of wireless audio transmission systems such as for example wireless microphones, in-ear monitors and chin strap headphones, there has in the meantime been a change over to embodying transmission systems of that kind with analog and digital functional units, that is to say on a hybrid basis. In particular relatively simple but robust analog FM transmission of the audio signals is combined with the advantages of digital signal processing. In the case of a conventional approach for a hybrid transmission system such as for example a hybrid microphone an inputted analog signal is digitized by an analog/digital converter and fed to a digital signal processing unit where the digitized signal is suitably processed and then converted back into analog signals again by a digital/analog converter. The converted analog signals are transmitted by an analog wireless FM transmission section and received by a suitable receiver. In the receiver the analog FM signal is digitized again and the original digital audio signal is reconstructed by means of a further digital signal processing unit. To improve or control the transmission a pilot tone is added to the digitized audio signal in the digital signal processing unit of the transmitter, serving to control the muting circuit (squelch) of the receiver. Accordingly the pilot tone and the coded audio signal are transmitted jointly by way of the wireless FM transmission section.
As general state of the arts attention should be directed to the documents DE 36 21 513 C2, DE 41 30 045 A1, DE 697 23 959 T2, U.S. Pat. No. 5,845,216 A, U.S. Pat. No. 5,222,250 A, U.S. Pat. No. 6,317,613 B1 and U.S. Pat. No. 6,219,559 B1.